This week, V is for verjus: a sour medieval staple that is suddenly having a
revival

It's commonplace for recipes to come and go in the cycle of food fashions. But for a stock ingredient to disappear from recipe books, only to be resurrected centuries later, is almost unprecedented.

This is what has happened to verjus. The acidic juice made from pressing unripe grapes or crab apples was something of a storecupboard staple in medieval kitchens. Not as acrid as vinegar, but sharper than wine, verjus possessed a much sought-after sourness, which made it an important ingredient. But when lemons and tomatoes and other such sour ingredients arrived in Europe, verjus soon dropped off the culinary map.

Recently though, verjus has experienced something of a revival, cropping up in some of Britain's top kitchens. The Fat Duck features 'Egg in Verjus' (c.1726) on its taster menu alongside the somewhat more molecular 'Verjus in Egg' (c.2013). Nigel Slater has a recipe for chicken with verjus, celery and cream, and Ottolenghi braises fennel, capers and olives in verjus.

Its recent revival means that verjus sounds new and exciting. But sour grape juice is an ancient ingredient. The earliest reference dates back to 71AD, where a Roman recipe cites three different types of grape juice: grape juice syrup, wine and verjus.

It was at the height of its popularity in the early medieval period, when the grapey flavours complimented the fruity, sweet-sour, spiced style of cooking. Verjus appeared in a recipe for grilled chicken with almond milk in the 1324 Catalan cookbook, Libre de Sent Sovi. A hearty slosh of verjus was added to a 'souppe despourveue' (improvised soup) in the 1393 French lady's guidebook Ménagier de Paris. In 1420 French chef Maître Chiquart used verjus in a German-style spiced pork broth called Broet d'Alamaniz, and in a cookbook written in 1560 by Dutch chef Gheeraert Vorselman, there are two recipes instructing cooks how to make verjus.

Sour verjus flavours weren't just restricted to savoury dishes though. In 1662 French chef Pierre de la Lune recorded the use of verjus in a sweet and sour tart 'aigre a douce'. This was replicated fifty years later by English chef, John Nott, who served it to The Duke of Bolton. Food historian Ivan Day has recreated the recipe for his historical cooking courses: "It's similar to a Tarte au Citron," he explains. "You add sugar to the verjus, and then reduce it to a thick syrup. Once it has cooled, mix in egg yolks, cream and spices, and then cook it in a blind-baked pastry case until it's set like a thick custard."

Not long after the publication of these recipes, verjus start fading from recipe books. Day observes that its marginalisation coincided with the arrival of tomatoes in Italy in the mid-16th century, as well as lemons becoming widely available in northern Europe - meaning that cooks were turning to other sources to introduce sour flavours to their dishes. "If you go to a grocer in a wine-growing region of France and ask for verjus, people often won't know what you're talking about," says Day. "It just disappeared".

Day is one of a group of small-scale producers who have been brewing their own verjus for decades, tweaking recipes from historical texts. He chose to go down the more English route of using crab apples, rather than grapes. "But there's no reason not to use English grapes," he says. "England is well positioned for making verjus. The inclement climate means that when we grow grapes they rarely produce sugar, so you get the right level of acidity for a good verjus."

The main person accredited with thrusting verjus back into the limelight is Australian vigneron and chef, Maggie Beer. It all started in 1984, when her vineyard had a bad harvest: "We were unable to sell our Rhine Riesling grapes," she explains. "I'd been coming across the magic word 'verjus', so making it seemed like the obvious next move."

Beer started tinkering with different verjus blends, and experimenting with their uses in the kitchen. In 2001 she released a recipe book, Cooking with Verjuice, with a follow-up in 2012 called Maggie's Verjuice Cookbook.

By this time, the verjus trend had travelled to other the New World wine producing regions. Terrasonoma is one of a handful of companies producing verjus in California's Napa Valley. The Verjuice Co. is based in the heart of South Africa's wine region and The Vine Co. produces verjus from grapes grown in New Zealand's Hawke's Bay.

One of the reasons for vitners' enthusiasm surrounding verjus is its benefit-cost ratio. "A lot of verjus is produced from ‘thinnings’ of the grape harvest, which happens much later in the process," Beer explains. "It offers further commercial viability, using what would otherwise go to waste."

'Thinnings' come from grapes which have been allowed to ripen, so they produce a product sweeter than Beer likes: "My love for verjus stems from its wonderful tartness or 'agresto' as the Italians would say." As a result, Beer's grapes are grown specifically for verjus production, so they can be picked early in the season before they ripen and sweeten. "In the case of my verjus, the producer’s personal preference plays a very big part," she laughs. "From the onset, my verjus was always made to suit my palate, with the hope that if I liked it others would too."

One of the simplest and most effective uses for verjus is for deglazing a pan.

2 tbsp oil

150g pork loin chop, bone out

1 medium-hot red chilli, halved

50ml verjus

Salt

Massage a little oil into the pork loin chop, and season with salt. Heat the remaining oil in a pan.

While the oil is coming up to temperature, use the heel of your hand to push half a chilli into each side of the pork loin chop.

Place the pork loin chop in the frying pan, and use the flat side of a mug to press it against the hot bottom of the pan. This will help embed the chilli, and give the pork lovely colour.

After three minutes, flip the pork to the other side, and press down on the other side for three minutes.

A thick pork chop may need a little extra cooking time. If that's the case, then add 50-100ml water to the pan. Cover and cook for a further 3-5 minutes. Remove the cover, and then allow the remaining water to evaporate.

Remove the pork loin chop from the pan, and leave to rest for five minutes. In the meantime, deglaze the hot pan with the verjus, using a wooden spoon to scrape up and stir in any browned bits in the pan.

Plate up the pork loin chop with vegetables, and pour the verjus 'jus' over the meat.